Pressure feeding of casting using a feeder head

ABSTRACT

A self-pressurizing feeder head vessel for pressure feeding molten metal into a casting mold is described. The feeder head vessel shown is a dome-shaped, fluid impervious shell with an open bottom, the shell being lined with green sand to define a feeder head cavity. A porous cylinder or an apertured tube is provided at the top of the vessel so that steam formed by heat in the green sand may flow through the cylinder or tube and downward into the feeder head cavity and thus apply pressure on the molten metal in the feeder head cavity to force additional molten metal into the casting mold during the shrinking period. Thus a method disclosed for applying pressure to the molten metal in the feeder head cavity is to vaporize the water in the green sand and apply the fluid pressure thereby generated to the molten metal, and thereby force the molten metal under pressure into the casting mold during shrinkage.

United States Patent [72] Inventor Wyman Curtis Lane 1469 W. Lane Ave.,Columbus, Ohio 43221 [21] Appl. No. 841,661 [22] Filed May 22, 1969Division of Ser. No. 678,231, Oct. 26, 1967,

Patent No. 3,513,904. [45] Patented Mar. 2, 1971 [54] PRESSURE FEEDING0F CASTING USING A FEEDER HEAD 7 Claims, 16 Drawing Figs.

[52] U.S.Cl 164/120, 164/285 [51] Int. Cl B22d 27/14 [50] Field ofSearch 164/ 1 19, 120,359, 360, 285, 349, 363

[56] References Cited UNITED STATES PATENTS 1,313,602 8/1919 Luxmore164/119X 1,533,474 4/1925 Shotton 164/119X FOREIGN PATENTS 128,6618/1948 Australia 255,158 l/1949 Switzerland Primary Examiner-Charles W.Lanham Assistant Examiner-R. Spencer Annear Attorney-Jerome R. Cox

ABSTRACT: A self-pressurizing feeder head vessel for pressure feedingmolten metal into a casting mold is described. The feeder head vesselshown is a dome-shaped, fluid impervious shell with an open bottom, theshell being lined with green sand to define a feeder head cavity.

A porous cylinder or an apertured tube is provided at the top of thevessel so that steam formed by heat in the green sand may flow throughthe cylinder or tube and downward into the feeder head cavity and thusapply pressure on the molten metal in the feeder head cavity to forceadditional molten metal into the casting mold during the shrinkingperiod.

Thus a method disclosed for applying pressure to the molten metal in thefeeder head cavity is to vaporize the water in the green sand and applythe fluid pressure thereby generated to the molten metal, and therebyforce the molten metal under pressure into the casting mold duringshrinkage.

II 111 11/ I] II PATENTEU HAR 219m SHEET 2 0F 4 1/1 1/ III/III] I I I II I I INVENTOR.

WYMAN C. LANE A TTORN E Y PATENTEUHAR 2191i 3565952 SHEET 3 [IF 4 as FIGIO INVENTOR. WYMAN C. LANE BY ATTORNEY PRESSURE FEEDING .OFCASTING USINGA FEEDER HEAD 1 This is a division of my application Ser. No. 678,231,filed Oct. 26, 1967, now Pat. No. 3,513,904 issued May 26, 1970.

BACKGROUND OF THE'lNVENTlON herein referred to as melt, from one or morechambers intoa'.

casting as it cools. These chambers, called feeder head cavities,are..usually located near the portion of the casting being fed, are influid communication with the casting mold; and serve to compensate forshrinkage of the melt as it solidifies and cools l in the casting mold.The metal within the feeder head cavity is called afeeder head, althoughit is often called a riser, a blind riser, or a shrink'bob. Usually afeederhead is cylindricalor dome shaped as determined by the shape ofthe feeder head cavity. a

When casting with feeder heads, melt enters the feeder head 1 cavity anda solidified layer chills around theouter surfacexof the feeder head,the-necessary runners andthe casting itself positionedin the adjacentcasting mold. The solidified layer is airtight and, therefore, unlessother provision is made, only the force-of gravity on the liquid portionof the feeder head,

called the feeding reservoir, will cause feeding of the melt" toward thecasting. Y

J. Williams in U.S. Pat: No. 2,205,327, and F. J. Mackett, Jr. in U.S.Pat. No. 2,295,227, point out some of the'difficulties of using unventedfeeder heads. Williams describes means for venting the feeder headcavity to the atmosphere'so that atmospheric pressure may additionallybe applied to feed melt. to the casting. Williams uses a porous rodextending from-"a.

point, in communication with the atmosphere, to a point within thefeederhead cavity. Mackettburns a combustible rod in the riser portionof his apparatus.

Because the application of a superatmospheric pressure to a feeder headallows the use of smaller feederheads and therefore leads to moreefficiency, two systemsfor applying such pressure were devised.

One system utilizes'superatmospheric gas pressure applied to thefeederhead from an external gas source.(e.g. a source of air pressure). Thissystem is typified by the U.S. Pat. Nos..to Ling 2,561,062 and toBilliar 2,568,428,,and by the: British Fat. to Metropolitan Vickers676,571. However, these systems require bulky and expensivegascontainers, hoses, regulators, and gages, and require extensivemanual observation and control.

The other system is typified by the U.S. Pat. Nos. to Campbell et al.2,439,450 and to Hardy 2,476,296. Hardy provides a volatizable metalsupported within the feeder head cavity. Other patentees use anencapsulated gas producing substance or a material which expands onignition to createa pressure on the feeder head. However, these priortypes do not provide a sufficient or controllable time delayforformation of a solidified layer of metal at the exterior of the feederhead to contain the gas produced. These prior types also do not allow asatisfactory rate of pressure increase. Breaks in their solidified layeraround the feeder head result in an immediate.

loss of gas pressure. Thecapsule materials used by some of thesepatentees add foreign materials to the feeder head ruining its scrapvalue. p

When pressure casting with feeder heads, a proper time delay beforepressurization followed by a proper rate of increase of pressure on thefeeder head is necessary to permit the solidification of asufficientlythick solidified layer around the exterior of the feeder head, thecasting and the runners. The solidified layer in the casting andrunnersmust be suffi ciently thick at all times to contain thepressurebeingapplied. Too much. initialpressure may burstthe solidified layerand result in a leak of molten metal through the solidified layer. Asand penetration-type defect on the surface of the casting will result.However, as the cast article cools and the solidified layer thickens, anincrease in pressure is desirable to adequately feed the melt tothecasting to compensate for shrinkage in the casting and to make itsound.

There is therefore a need. for a feeding system which will providecontrolled time delay between the introduction of the melt into thefeeder head cavity and the development of pressure. This time delayallows a sufficiently thick solidified layer to chill around theexterior of the runners and the casting to contain the applied pressure;

There is a need for a feeding system which will provide a controllable,initially small,'and smoothly increasing gas pressure to a feederhead,.with a time delay between the pouring of theliquid metal and theinitial development of such pressure.

OBJECTS it is thereforean object of my invention to provide an improvedpressure feeding system for use in the production of castings.

Another object of my invention is to provide apressure feeding apparatusfor castings and a method which avoids an uncontrollable, prematureburst of the solidified layer and loss of pressure, but rather providesatime delay between the in troduction of .melt into the feeder headcavity and the development of pressure.

Another object of my invention is to provide for-a method.

of casting with which. a low controllable fluid pressure is appliedinitially to a feeder head and in which the fluid pressure is smoothlyand controllably increased so that the end result is a casting with'aminimum of defects.

A still further object of my invention is to provide a feeding apparatusand method for casting wherein an initially steadily increasing fluidpressure is applied to the feeder head without loss of pressure in thetime period before a solidified'layer of sufficient strength andthickness to hold such pressure chills around the feeder head.

A still further object of my invention is to provide a feeding apparatusfor castings which does not require complex or expensive equipment,which can easily be handled by the ordina= ry foundry worker, and whichcan be reused; and to provide afeeding method which iscontrollable,simple, and easily'performed.

Further objects and'features of my invention will be apparent fromtthefollowingspecification and claims when considered in connection with theaccompanying drawings illustrating several embodiments of my invention.

SUMMARY OF THE INVENTION I have found that these and other objects maybe attained'in a devicefor use in conjunction with a feeder head cavityand with a temperature-responsive fluid pressure producing agent in thesupplying of melt to a casting mold, the devicecomprising: asubstantially fluid impervious shell having, in a selected position, anopen bottom to permit entry'of melt into the cavi-.

ty, said shell adapted to receive a refractory inner lining for ing asubstantially fluid impervious shell having, in a selected 1 position,an open bottom to permit entry of melt into the cavity; a. refractoryinner liningin at least a portion of the. shell,

and a heat-responsive fluid. pressure-producing agentcontainednby therefractory; wherein fluid pressure is generated. by heat transfer: tothe agent, andv the pressureis directed:

toward. the supplying of melt toward the casting mold.

I have further found that these objects may be attained substantiallyautomatically by a method for applying desirable pressure comprising thesteps of (a) vaporizing the water in green sand; and (b) effecting theapplication of the vapor pressure to the feeder head.

These objects may be attained in a feeder head device having its fluidpressure producing agent positioned entirely outside of the feeder headcavity but in thermal connection to the feeder head.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view in vertical sectionof a casting apparatus equipped with a casting mold cavity and feederhead vessel devices, all constructed according to my invention;

FIG. 2 is a view in horizontal section of one of the feeder head vesseldevices shown in FIG. 1, and is taken substantially along the line 2-2of FIG. 1;

FIG. 3 is a view in vertical section of a feeder head vessel deviceconstructed according to my invention, taken substantially along theline 3-3 of FIG. 2 but shown on an enlarged scale;

FIG. 4 is a view in vertical section of another embodiment of myinvention;

FIG. 5 is a view in vertical section of another embodiment of the feederhead vessel device of my invention;

FIG. 6 is a view in vertical section of another embodiment of myinvention;

FIG. 7 is a view in vertical section of another embodiment of myinvention;

FIG. 8 is a view in vertical section showing details of a vent and fluidconducting shaft for use in an embodiment of my invention;

FIG. 9 is a view in vertical section of an alternative vent and fluidconducting shaft for use in an embodiment of my invention;

FIG. 10 is a view in vertical section of an alternative vent and fluidconducting shaft for use in an embodiment of my invention;

FIG. 11 is a view in vertical section showing details of a chill sealfor use in an embodiment of my invention;

FIG. 12 is a view in vertical section showing details of an alternativechill seal for use in an embodiment of my invention;

FIG. 13 is a view in vertical section showing details of an alternativechill seal for use in an embodiment of my invention;

FIG. 14 is a plot of solidified layer depth as a function of time;

FIG. 15 is a plot of solidified layer depth as a function of refractorythickness; and

FIG. 16 is a plot of total end pressure as a function of waterpercentage in the sand refractory.

In describing the preferred embodiment of the invention illustrated inthe drawings, specific terminology willbe resorted to for the sake ofclarity. However, it is not intended to be limited to the specific termsso selected, and it is to be understood that each specific term includesall technical equivalents which operate in a similar manner toaccomplish a similar purpose.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Structure A casting apparatusas shown in FIG. 1 comprises a flask 10 containing compacted sand 12.The sand is shaped by conventional means to provide cavities which forma sprue 14 for the introduction of melt, a runner 16 connected to thesprue l4, and runners 18 connecting a casting'mold cavity 20 to feederhead cavities 22 formed in feeder head vessels 23 and 29. The dashedline 24, conformably within these cavities, generally indicates theinner limits of a solidified layer which forms during the castingprocess around the exterior of the melt in the cavities.

One of the feeder head vessel devices constituting a preferredembodiment of my invention is shown in greater detail in FIG. 2 and FIG.3. The feeder head vessel, indicated generally by 29, comprises asubstantially fluid impervious shell 30 with an open bottom and arefractory 32 which lines the inside of the shell 30 and which, in theembodiment ll prefer, is green sand and has distributed within it afluid pressure producing agent to be described more fully later. Iprefer that the shell 30, as well as the refractory 32 lining it, bedomeshaped. However, theexact shape of the shell 30 is not critical, andmany other shell shapes could be used. For example, I have illustrated abox-shaped shell 30 and refractory 32 in FIG. 6. The shell 30 may bebolted, by bolts such as 34, to a portion of the flask, but this isunnecessary for ordinary applications of my invention.

The shell 30 must be substantially fluid impervious. It must be able toretain fluid under a pressure which is sufficient to properly pressurizea feeder head in the manner described below. The shell 30 may beprovided with a vent 40 to permit the air, displaced by the rising meltlevel during pouring, to escape from the feeder head cavity 22. Such avent must chill closed soon after the melt contacts it or be providedwith some other sealing means. Alternative vent structures are describedlater.

The refractory 32 is positioned conformably within (i.e., lines) theshell 30. The innermost surface of the refractory forms a boundary 36 ofthe feeder head cavity 22. Although the boundary need not necessarily beshaped similarly to the shell 30, it must define a feeder head cavitywithin the shell. I prefer that the refractory 32 be in contact with theshell 30. However, another material could be interposed between therefractory 32 and the shell 30. For example, some types of fluidpressure-producing agents could be so interposed rather than beingdistributed within the refractory.

For the refractory 32, I prefer sand, especially green sand. Othermaterials such as porous ceramic would work in an equivalent manner. Iuse the word refractory to indicate any material which may be formedinthe desired shape within a shell 30, which can withstand the temperatureof the melt, and which will not substantially deteriorate or produce asubstantial reaction when melt is poured into the feeder head cavity.Some materials might be satisfactory as a refractory for certain lowtemperature melts while not being satisfactory for higher temperaturemelts. In the preferred embodiment, the same refractory is porous andpermeable so that a fluid pressure-producing agent may be distributedwith it and so that fluids may pass through it.

A fluid conducting shaft 38, near the top of the feeder head vesselextends from within the refractory 32 down into the feeder head cavity22. I prefer a porous rod conducting shaft such as 38a shown in thesmaller feeder head vessel device 23 in FIG. 1. Other structures, suchas a thin cross section extension of the refractory or a hollow tube(shown in vertical section in FIG. 1 and FIG. 3 and in horizontalsection in FIG. 2), would be substantially equivalent. The hollow tube38, as shown, is formed at its upper end with apertures 39.

In order to provide a fluid pressure seal between the shell and thesolidified layer in the casting, a chill ring 37 (see FIG. 3) may bepositioned around the lower edge of the shell 30. Alternative chill sealstructures are described later.

In FIG. 4, I show an embodiment similar to that shown in FIG. 1 exceptthat the feeder head vessel device is shown positioned in a conventionalflask l0.and is buried within the sand 12, unexposed and inaccessible.

The embodiment of FIG. 5 is substantially equivalent to the embodimentshown in FIG. 3. In addition to the structure shown in FIG. 3, an innerliner 33 is provided which separates the feeder head cavity 22 from therefractory 32. Thermally, however, the inner liner 33 is substantiallyan extension of the feeder head and therefore considered to be withinthe feeder head cavity and equivalent to the outermost layer of thefeeder head itself.

In FIG. 6, there is shown an alternative embodiment in which the shell,the feeder head cavity, and the feeder head are all box-shaped orrectangular in cross section.

. Another alternative embodiment is shown in FIG. 7 in which the fluidimpervious shell 30 is lined with a nonporous refractory 32 such as aglazed ceramic. A fluid pressure producing agent is interposed along theinterface 35 between the shell 30 and the refractory 32.

Other alternative embodiments, whichare not shown, can have refractoryonly partly lining shell 30. Only the upper half or only one side, forexample, could be so lined with refractory.

l have found it desirable to vent the feeder head cavity to theatmosphere during the entry of melt into the feederhead cavity as statedabove.

In FIGS. 8, 9, and 10, I showsome example vents 40 which are each formedby a hole in the fluid impervious shell 30.

I prefer that the vent be located near the top of the shell 30, arid inFIG. 8 I show a vent 40 which has a fluid conducting shaft 38 positionedbelow it. The fluid conducting shaft 38 shown is porous for. providingfluid communication between the refractory 32 and the feeder headcavity. The shaft38 is also provided with a passageway 42 providingcommunication between the feeder head cavity and the vent 40.

In FIG. 9, I show an alternative vent 40 and an alternative fluidconducting shaft 38. The vent 40 is a hole through the shell 30 and therefractory 32. Thus it is'not necessary that the vent be above the fluidconducting shaft.

The fluid conducting shaft 38, shownin FIG. 9, is a conical Thealternative fluid conducting shaft shown in FIG. 10 is a.

hollow cylinder with tapered walls and is formed of the same refractoryas that lining the shell 30. The vent 40 is a pipe 44 threadedly,engaged tothe shell 30 to provide fluid communi-' cation between thefeeder head cavity and the atmosphere through the refractory 32. Thepipe 44 is provided with a hand operated or automatic valve (not shown).

In FIGS. 11, 12, and 13,1 show alternative chill ring structures. Ineach of these embodiments, thechill'ring 37 is an extension of the shell30 and surrounds the feeder head cavity; The chill ring serves to assurerapid freezing of melt to provide a fluid pressure seal between theshell30 and solidified layer which freezes around the exterior of thecasting and the runners.

Operation Prior to the introduction of melt into the sand mold shown inFIG. 1, the entire mold is at room temperature (e. g.,.20 C). Melt ispoured into the inlet sprue 14 until all cavities are substantiallyoccupied by melt, includingthe cavity whichis the feeder head cavity 22.Air escapes from the feeder head cavity through the vent 40. When meltenters the vent 40 and contacts the shell 30, it will freeze to form aplug in the vent. The contact of the melt, forming the feederzhead, withthe boundary 36 of the feeder'head cavity causes the water in the greensand refractory 32 near the boundary 36 to vaporize. This vapordiffusesoutwardly away from the boundary 36 and toward the shell 32. t t

The vapor will initially condense at a point between the boundary 36 andthe shell 30 at which the green sand temperature is less than or equalto 100C. As a result of the changing temperature gradient acrosstherefractory, the condensation point moves outwardly toward the shellwhile increasing the water concentration of that point in therefractory. Thus the introduction of melt into the feeder head cavitycreates a water saturated envelope surrounding the feeder head. whichmigrates away from the feeder head, within the refractory 32, towardtheshell 30.

Eventually the migrating water envelope contacts the shell and is.heated to the boiling temperature. Steam is produced and the pressurestarts to rise. This steam diffuses outwardly into the green sand. Thediffusion of this steam provides the desired initial low pressure. Thesteam is forced into the shaft 38 through the pores of the shaft.Pressure is exerted on the feeder head through the fluid conductingshaft'38. As more heat is transferred to the device, its temperaturerises and the pressure on the feeder head increases.

Theresulting pressure and its variation in time for any given structurecan be determined easily. However, it can be regulated by the initialwater content of the refractory, the

geometry of the refractory, and the density and heat conduc-v tivity ofthe refractory. Other important parameters are the melting temperatureof the metal being poured and the heat of fusion of the metal. A verydetailed analysis of all the controlling parameters would include muchmore than this simple example, but it must be emphasized that theconcept would not change. i

The time delay, during which no pressure is applied, is sufficient to.allow the necessary solidified layer 24 to chill around the exterior ofthe melt. It is essential that a solidified layer be chilled and formaroundthe runners andin the casting. How ever, it is clearly. notnecessary that a solidified layer be formedon the exterior of the feederhead because the shell 30 fully contains the pressure on the feederhead.

A suitable time for initial pressurization ischosen on a basis of themetal being poured, the depth of solidified skin desired in the castingbefore pressurization, and the heat transfer characteristics of themolding sand. FIG. 14 shows the theoretical time lapse required for mildsteel and aluminum bronze castings plotted against the depth ofsolidified skin. The slope of these curves will vary slightly with theheat transfer characteristics of the moldingsand. These curvesare basedon an average foundry molding sand.

It should be remembered that the data given in this description ismerely the currently best analysis available. The data is given forpurposes of illustration, and I do not intend to represent that it isaccurate. It has not yet been experimentally verified and therefore issubject to modification.

The thickness of the refractory layer required to give the proper timedelay is dependent on the metal poured, and the heat transfercharacteristics at the refractory layer, assuming, for simplifying theanalysis, that the solidified layer in the feeder head at initialpressurization is the same as in the castmg.

FIG. 15 shows a plot of the refractory layer thickness as a function ofthe solidified layer thickness for mild steel and aluminum bronze. Thecurves are based on sand as the refractory material used in the device.Here again the curves are derived theoretically and will change slightlywith sand and molding practice.

The total end pressure achieved in the casting is controlled, for agiven head geometry and refractory thickness, by the final meantemperature of the water vapor in the pressurized head and the amount ofwater originally added to the refractory. A reasonable estimate for themean gas temperature is onehalf the melting temperature on the absolutescale.

FIG. 16 is a plot of the percent water in the refractory versus endpressure for several mean gas temperatures. This plot was made for acylindrical shaped feeder head 12 cm. in diameter by 30cm. long with arefractory thickness of 0.793 cm. and a frozen layer thickness of 0.3cm. in the head and in the casting.

The development of pressure will not normally cause the feeder headvessel'to separate from the runners and casting because at all times thestrength of the solidified layer, surrounding the casting and runnersand frozen to the chill ring,

will be sufficient to secure the feeder head vessel to'the Fluidpressure-producing agents other than water can be used. Many such agentsinvolve a vaporizable substance proceeding through physical changesanalogous to the behavior of water. In fact, any vaporizable materialwith a vaporization temperature below the melt temperature would producesome results according to my invention. For example, powdered zinc couldbe distributed throughout the refractory to provide a useful pressure onthe feeder head and to obtain a different time delay. Alternatively, asa further example, clay or other material containing water ofcrystallization would give desirable results.

It should also be apparent that it would not be necessary that all theheat which causes the fluid pressure be derived.

from the melt. Auxiliary heating means, such as burners or heatingcoils, could be attached to my device to provide heat for vaporizing thewater in the green sand.

Similarly, solid or liquid chemical materials which, upon being heated,evolve a gas, can be used as fluid pressure producing agents.

With the embodiment shown in FIG. 7, a nonporous refractory 32 could beprovided. The fluid-producing agent could be interposed between therefractory 32 and the shell 30. Heat conduction through the refractorywould provide a time delay. The gas produced would diffuse along theinterface between the refractory and the shell to the top of the shelland then through the fluid conducting shaft 38.

Another alternative mode of operating my invention would involve adevice similar to that shown in FIG. wherein the refractory 32 and thefluid pressure-producing agent comprises a liquid with a high thermalexpansion, such as salt flux. Upon transfer of heat to the liquid flux,the flux would expand and a portion of it would pass through a fluidconducting shaft 38 such as that shown in FIG. 3, and apply itsfluid'pressure to the feeding reservoir.

It is to be understood that while the detailed drawings and specificexamples given describe preferred embodiments of my invention, they arefor the purposes of illustration only, that the apparatus of theinvention is not limited to the precise details and conditionsdisclosed, and that various changes may be made therein withoutdeparting from the spirit of the invention which is defined by thefollowing claims.

Iclaim:

1. A method for applying superatmospheric pressure to a casting moldfeeder head within a green sand feeder head cavity comprising the stepsof:

a. filling said feeder head cavity with molten metal during casting;

. forming a solidified layer on the cast metal;

. vaporizing the water with the green sand at a sufficiently slow ratethat said solidified layer does not burst, and thereby release thepressure; and

d. subsequently directing the water vapor pressure, formed within saidgreen sand lining, into said feeder head cavity for effecting theapplication of the vapor pressure directly to the molten metal containedin the feeder head cavity.

2. A method according to claim 1 wherein after vaporizing the waterwithin the green sand there are performed the further steps ofcondensing the water vapor and then vaporizing again the condensedwater.

3. The method according to claim 1 wherein the water is vaporized byheat transferred from the feeder head.

4. A method for applying superatmospheric pressure to a casting mouldfeeder head which is contained in a feeder head mold, the feeder headmold defining a feeder head cavity comprising refractory feeder headwalls within a fluid impervious pressure containing shell surroundingthe feeder head mold and the feeder head, the methodcomprising:

a. positioning a temperature responsive fluid pressure producing agentbetween the shell and the feeder head cavity wall;

b. filling said feeder head cavity with molten metal during casting;

c. forming a solidified layer on the cast metal;

d. heating the agent to increase the pressure in the shell at asufficiently slow rate that said solidified layer will not burst andthereby release the pressure; and e. directing the pressure produced bysaid agent into the

1. A method for applying superatmospheric pressure to a casting moldfeeder head within a green sand feeder head cavity comprising the stepsof: a. filling said Feeder head cavity with molten metal during casting;b. forming a solidified layer on the cast metal; c. vaporizing the waterwith the green sand at a sufficiently slow rate that said solidifiedlayer does not burst, and thereby release the pressure; and d.subsequently directing the water vapor pressure, formed within saidgreen sand lining, into said feeder head cavity for effecting theapplication of the vapor pressure directly to the molten metal containedin the feeder head cavity.
 2. A method according to claim 1 whereinafter vaporizing the water within the green sand there are performed thefurther steps of condensing the water vapor and then vaporizing againthe condensed water.
 3. The method according to claim 1 wherein thewater is vaporized by heat transferred from the feeder head.
 4. A methodfor applying superatmospheric pressure to a casting mould feeder headwhich is contained in a feeder head mold, the feeder head mold defininga feeder head cavity comprising refractory feeder head walls within afluid impervious pressure containing shell surrounding the feeder headmold and the feeder head, the method comprising: a. positioning atemperature responsive fluid pressure producing agent between the shelland the feeder head cavity wall; b. filling said feeder head cavity withmolten metal during casting; c. forming a solidified layer on the castmetal; d. heating the agent to increase the pressure in the shell at asufficiently slow rate that said solidified layer will not burst andthereby release the pressure; and e. directing the pressure produced bysaid agent into the feeder head cavity for effecting the application ofthis pressure directly to the molten metal contained in the feeder headcavity.
 5. A method according to claim 4, wherein the heat is suppliedfrom melt which enters the feeder head mold to form the feeder head. 6.A method according to claim 5, wherein the agent is distributed in therefractory.
 7. A method according to claim 6, wherein the agent iswater.